Question: does userspace conversion support images from local image store

### What is the version of your Accelerated Container Image

_No response_

### What would you like to be added?

I was trying out [userspace conversion](https://github.com/containerd/accelerated-container-image/blob/main/docs/USERSPACE_CONVERTOR.md), and it seems the conversion works on an image in a remote registry, and the converted image is also in the remote image registry. If I have an image in my local store, and want to convert it and keep the converted image in the local store, I don't see an option to do that.

This command works and the converted image is pushed to the remote registry:
```
/opt/overlaybd/snapshotter/convertor -r my.registry.com/repo1/overlaybd/redis -u user:password -i 6.2.6 --overlaybd 6.2.6_obd
```

If I have an image in my local store, and try to convert it, it doesn't work:
```
/opt/overlaybd/snapshotter/convertor -r overlaybd/redis -i 6.2.6 --overlaybd 6.2.6_obd
```
I got an error like:
```
ERRO[0000] failed to create overlaybd builder: failed to resolve reference "overlaybd/redis:6.2.6": failed to do request: Head "https://overlaybd/v2/redis/manifests/6.2.6": dial tcp: lookup overlaybd on 127.0.0.53:53: server misbehaving
```

Is this expected?

### Why is this needed for Accelerated Container Image?

Ask to support converting an image from the local image image store in the userspace.

### Are you willing to submit PRs to contribute to this feature?

- [ ] Yes, I am willing to implement it.